Microphone



July 3, 1,945.. Y c, B, FlsHER 2,379,514

- MICROPHONE Filed Sept. 30, 1942 AT ToRNEY Patented July 3, 1945 UNITED STAT-Es. PATENT OFFICE v @2,379,514 n p f MICROPHONE d .CllarlresrByFishen Washington, D. C. .Application September 30, 1942, Serial No.v 460,229 y polaires. (ci. 179-187)l l This invention relates to microphones for use by busyo-perators within noisy vehicles, such' 'as aircraft Aand tanks, and particularly ltowards substantiallyimprovingr the `resultant signal-tonoise ratio. l A

Attempts have been made for a considerable period to provide a practicaland eflicientrnicrophone for use by aircraft pilots, tank' operators, and the like, that is readily used and Aprovides ,a high signal-to-noise ratio despite a noisy backrequired extra pre-amplication. Also,` the mi-- crophones were suspended'before the mouth of theoperator. Such were impractical since the microphone or its xture interfered with the" operators movements, and particularlyv since such1 microphones valso responded to the surrounding engine noises which were co-mingled with the'voice signals, and deteriorated the vresultant signal -intelligibility- In accordance with the presentfinvention I provide asmall light-weight microphone combined with a projecting stem that is placed in the mouth and gripped by` the teeth. The stem c ont'ainsa sound channel or passage communicating with the sensitive element of the microphone. microphone unit is unobtrusive and in nomanner interferes with the usual activities or -duties of the operator. The small, light-Weight microphone `unit of the present invention is readily supported by the mouth, isrnottirin'g on `the operator, and does not interfere with his speaking. Most importantly,` the resultant speech -signals are of good quality accompanied with negligible background noise. M `4 'd 4 l I `have determined the soundy pressure of The.

Such attempts included microphonesl y stem. The'result is an overall improvement in signal-to-noise pressure ratio of theorderof A'at least twenty to one, or'the lorder `of twenty'six decibels. The microphone system of the invention is thus verypracticahinservice, andjprof duces clear `voice signals 4'of relatively ygreater power and signal-to-noise ratio than prior microphones. y Y f Y It is ,accordingly an object of my present in-V vention vto provide a novel Amicrophone 4arrangement that affords a substantial improvement in the'resultant signal-to-noise ratio whenused in noisy locations, such asin fighter planes or tanks,

Another object ofthe present invention is to provide a novel microphone tliatfis readily supported bythe operators mouthin ajmanner'so as not to interfere with vhis speaking.

A further object of the present. invention is to provide a A'small lightweight microphone that is readily held in the operators mouth,l and isnot subject to background noises so as to afford high signalfto-nose ratio voice signals.

These and further .objects and auvantageso'f vention in positionin `the operators mouth; Fig.

2 is an enlargedl horizontal cross-sectional yiew of the microphone unit, partly in elevation; Fig.

speech, at the position within;t he mouthr and behind the teeth, to be alooutvthe order of twice the corresponding sound pressure just outside of the mouth in front of the lips, although theA dis- Also, the

3 is a vertical cross-sectionalview ofthemicrophone unit',.partly in elevation; Fig..4 is a `front elevational-view of the microphone; and Figs.. 5 and 6 are respective elevational and top views of the microphone stem.-

The microphone unit I0 is provided Witha pro- `vjectingstem Il which, as shown in Fig. 1is

adapted to l.be gripped between thel teeth I2 by 1 channel'lll within the stem vl Iconstitutes a sound passage between the mouth;cavity, where the crophone `cable I6 of iiexiblewiresr electrically connects the microphone unitV I U to the amplifier or soundapparatus, which, like the circuitconnections for the microphone, are 'conventional and are'not-shown. g The microphone unit if! comprises a casing I1 within which is mounted the sensitive microphone element I5, as for instance a conventional carbon button, an electrodynamic microphone unit, or equivalent sound translating element for converting the sound waves conducted to it through stem II into corresponding electrical currents. A threaded cover plate I8 coacts at I9 with casing IIto form a closure for the microphone I5.

Ihe stem II contains a shoulder at 2D that is press-fitted into an opening in casing II directly in front of the sensitive portion or diaphragm of the microphone element I5. The channel I4 provides a sound passage between tip I3 and microphone element I5, and terminates as a hole or outer opening at 2| in the` tip. Two additional channels 22 and 23 are drilled in tip I3, transverse to the direction of channel I4, and provide four outer openings at tip I3.

The stem I I is designed to fit comfortably in the mouth and be Well supported and gripped by l the teeth with the lips closed around it. The horizontal section of the stem is preferably wider than the vertical height so that the microphone is stably held in the mouth. As seen in Figs. 5 and 6, the stem is rather flat, and the tip I3 projects away from the body portion to prevent longitudinal outward displacement or slippage of thc stem from the teeth.

The group of openings provided by the channels I4, 22 and 23, alords openings through which the sound pressures generated within the mouth are directly communicated to the microphone element I5. The plurality of holes at stem tip I3 insures a continuous unattenuated communication of the sound pressures from the mouth to the microphone I5, despite the possibility that the tip of the tongue may temporarily close one or more of the openings. At least some of the openings will always be exposed and provide continuous normal operation of the microphone. The stable support afforded by the preferred stern I I permits the microphone to be readily held in position while the operator is talking in a normal manner. The upper and lower sets of teeth I2 are separated' by at least about V8", and the speech operation is substantially uninhibited. The projecting portions of the stem prevent it from sliding out of the mouth, and the teeth need not be gripped tightly, but held loosely thereabout. somewhat in the manner 0f talking while smoking a pipe.

The stem I I is preferably constructed of a composition or plastic material for strength and lightness.y The material should have a neutral taste and toward this end I prefer such materials as clear cellulose acetate, a phenol formaldehyde plastic, or the like. The microphone casing IT, i3 is likewise also of a strong but light composition or plastic material. Also, I have foundthat sufficiently sensitive microphone elements I5 are preferredv casing of about 5/8" to 3/4" in diameter, and about /s" to 1/2 in thickness. The stem II is preferably of the order of 3X1" long from end to end, and about 5/8" wide at the widest section across tip I3, tapering down to the microphone casing Ilto a width of aboutl I'have found such dimensions to be practical in service, and the construction is such as to make the microphone small, light, comfortable and unobtrusive.

Also, I have found that the preferred dimensions', and the construction pursuant' to the present invention, provide a,y microphone unit that is emcient and practicalin the eld. This. microphone, using a carbon-button. or other form o f microphone element I5, is practically unadected by noises occurring within a tank or aircraft in military operation. The higher pressure sounds within the mouth cavity behind the teeth are directly communicated to the microphone element. Also, the lips closed about stem II shield the speech sound waves to the microphone element from the local parasitic noises. The overall improvement in the signal-to-noise ratio is of the order of 26 `decibels as compared to a conventional microphone unit held in position directly in front of the mouth. Also, the intelligibility of the resultant sound waves reproduced by the microphone system of the present invention is superior to the open type of conventional microphones that are subjected to the background noises in service.

Although I have described a preferred embodiment and construction for the microphone of my present invention, it is to be understood that variations thereof may be practiced without departing from the broader spirit and scope of the invention as defined in the following claims.

Having thus described my invention, what I claim is: f

i. A microphone of the character described comprising a casing containing a sound translatingmicrophone element, and a stem extending from an opening in said casing, said stem having a rst through channel that communicates with the sound sensitive portion of said microphone element, the end tip portion of said stem being adapted to lit into ones mouth and held gripped between the teeth, and said stem having a second channel in the end tip portion thereof extending transversely oi and intersecting with said first channel.

l2. A' microphone of the character described comprising a casing containing a sound translating microphone element, a fiat stem extending from an opening in said casing, said stern having a longitudinal channel that communicates to the sound sensitive portion of said microphone element and also havinga. second channel in thev terminal portion thereof extending transversely of 4. A. microphone of the character described A commercially available so as to be fitted into a P Comprising a nght'weght' Casing Containing 9* sound translating microphone element, a lightweight stem extending from an opening in said casing, said stem having a first through channel that communicates with the sound sensitive portion of said microphone element, the tip of said stem being adapted to t into onesmouth and 

